Pressure switch for fuses



y 3, 1952 J. RABINOW PRESSURE SWITCH FOR FUSES 2 SHEETSSHEET 1 FiledAug. 5, 1949 gwuon'fo'b Jucub Hnbinuw zw wwmg g May 13, 1952 J. RABINOWPRESSURE SWITCH FOR FUSES Filed Aug. 3,- 1949 2 SHEETS-SHEET 2 gwwcmfoma 22 wJnED b Huhinuw Patented May 13, 1952 UNITED 'iATS PATENT FFIEPRESSURE SWITCH FOR FUSES (Granted under the act of March 3, 1883, asamended April 30, 1928; 370 O. G. 757) The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes without the payment of any royalty thereon.

My invention relates to arming devices for electrically operated fusesfor ordnance projectiles, such as bombs or artillery shells. By anelectrically operated fuse, I mean a fuse in which the final firing isaccomplished by or requires the closing of, an electric circuit in thefuse.

In ordnance fuses it is essential to provide the utmost degree of safetyagainst abnormal conditions such as shocks which might occur in handlingor transportation, and to make the fuse responsive only tothoseconditions which occur uniquely when the projectile bearing the fuse hasbeen launched against a target in actual use, so that only when the fuseis subject to these conditions can it be armed. One condition common toboth bombs and shells is velocity relative to the ambient atmosphere,since the projectile is extremely unlikely to encounter velocities ofthe order of magnitude which occur when it is in flight after launching,except when it actually has been launched or fired.

It is an object of my invention to provide a fuse which is uniquelyactuated by high velocity motion relative to its ambient atmosphere andwhich is' unaffected by shocks or high acceleration or deceleration suchas might occur from dropping onto a hard surface or being struck byanother projectile. It is also an object to provide this feature in asimple, inexpensive, foolproof and relatively tamper-proof device whichis positive and definite in operation.

The specific nature of the invention as well as other objects andadvantages will clearly appear from a description from a preferredembodiment in the accompanying drawings in which:

Figure 1 is a longitudinal axial sectional view of a fuse embodying myinvention showing the principle of operation.

Figure 2 is a sectional view taken on line 2-2 of Figure 1.

Figure 3 is a view similar to Figure 1 showing a bimetallic switchelement instead of a simple pressure responsive element.

Figure 4 is a view partly in section of a fused projectile responsive totemperature rise only.

In the drawings I is the nose of a fuse adapted to be threaded at 2 intoa projectile such as a bomb or a shell 3 and provided with a threadedportion 4 adapted to receive a threaded base element 5 which can also bescrewed into the body portion of an electric fuse 6 which may be of anyJacob Rabinow, Washington, D. 0., assignor t0 the United States ofAmerica as represented by desired or known type requiring the closing ofan electric circuit for arming the fuse. This electric circuit isrepresented by leads '5, connected to terminals 8 which are adapted tobe bridged by a circular dished snap disc 9 to close the circuit to armthe fuse.

Snap disc 9 has two positions as shown in the dotted and solid linesrespectively. In the unarmed position the switch will of course be inthe center raised position shown by the solid lines. The snap diaphragm9 is supported concentrically between two resilient rings I! and i2which may be of rubber or of similar resilient material undercompression by screwing down the threaded member 5.

The diaphragm 9 is clamped between rings H and [2 at a radiusapproximately two thirds the total radius of the diaphragm so that themass of that part of the diaphragm radially beyond the clamping means isapproximately equal to the mass of the part within the clamping rings;ther fore ordinary shocks will not close the ring as they act on abalanced member which is also resiliently supported by the rings. Shockforces thus tend to balance out around the rings as a pivot. Opening [0which is preferably located in the nose of the fuse may have a needlevalve l3 for controlling the effective size of aperture Hi. Thisaperture leads to pressure chamber iii. A time delay is thus provided byrequiring a longer or shorter time to build up a critical pressure inchamber it according to the setting of valve Hi When the projectile isin flight.

The operation of the device should be self evident from the abovedescription. When the projectile is in flight, due to the increasedatmospheric pressure on the nose thereof air flows down the passage l9past needle valve I3 and into chamber I6. As the resilient rings H andI2 form a tight seal, the pressure in chamber l6 acts only upon thecentral portion of the diaphragm 9 and when this pressure reaches apredetermined amount, the diaphragm is snapped down into circuit closingrelationship, with the contacts 8. This action is positive and certainand since the contacts are in a closed chamber, they will remain cleanand in good condition until ready for use.

In Figure 3 the diaphragm is dimensioned and mounted exactly as inFigure 1 but in this case it is constructed as a bimetallic snap disc 9.This type of construction is old and well known for use as athermostatic switch element per se, but in the device shown it is madeuse of in a switch responsive to both pressure and temperature. Thetemperature in this case would result from the relatively rapidcompression of gas in chamber [6, and this can be pre-set so that onlywhen the pressure rises at a rate corresponding to what will occur whenthe projectile is correctly launched and properly in flight will thecorrect combination of pressure and temperature be present which willsnap the diaphragm to close the switch.

Figure 4 shows a rocket having a warhead 2| and a combustion chamber 22wherein the rocket propellant is contained to propel the missile.Between the warhead and combustion chamber is a switch chamber 23containing a balanced bimetallic snap switch element 24 in all respectssimilar to switch 9 of Figure 3, except that it is not arranged to beaffected by air pressure, but by temperature change only. When therocket is launched, the heat of combustion in chamber 23 will eventuallyreach the point for which the bimetallic element 24 is set and it willsnap over to bridge terminals 25 to arm the fuse generally indicated at26. 7

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in construction within the scopeof my invention as defined in the appended claims.

I claim:

1. In an electric fuse for projectiles, a safety arming switch havingcontact means, an actuating member for engaging said contact means toclose the switch, said actuating member comprising a dished flexiblesnap disc capable of being flexed into either of two dish-shaped forms,supporting means engaging said disc circumferentially at points on aperimeter defining within it substantially one-half of the mass of thedisc, whereby the disc is balanced against inertia forces actingdirectly thereon, said disc being arranged, when flexed into one dishedposition to close the switch and when flexed into the alternate dishedposition to open said contact means.

2. In an electric fuse for projectiles a safety arming switch havingcontact means, an actuating member for bridging said contact means toclose said switch, said actuating member comprising a dished flexiblesnap disc capable of be ing flexed into either of two stable dish shapedforms, supporting means engaging said disc circumferentially at pointsat a radius substantially two thirds the total radius of the snap discwhereby the disc is balanced against inertia forces, said disc beinginitially flexed to open circuit position on said supporting means, achamber having a portion of said disc as part of the wall thereof, saidportion comprising a central area of said disc with respect to saidsupporting means, and an aperture leading from said chamber to theambient atmosphere, said disc being arranged when flexed to itsalternative dished position to bridge said contact means to close saidsafety arming switch.

3. The invention recited in claim 2, wherein said flexible snap membercomprises a bimetallic temperature responsive element constructed andarranged to flex into the switch closing position only upon theattainment of a predetermined combination of temperature and pressurerise in said chamber.

4. In a projectile having a nose portion a safety arming switch havingcontact means, an actuating member for engaging said contact means toclose the switch, said actuating member comprising a snap disc capableof being flexed into either of two dish-shaped forms, a chamber in saidnose portion having a portion of the said disc as part of the wallthereof and.,

an elongated aperture leading from said chamber to the ambientatmosphere.

5. The invention as set forth in claim 4 wherein said snap disccomprises a bimetallic temperature responsive member located to flexinto switch closing position upon the attainment of a predeterminedcombination of temperature and pressure rise.

6. The invention as set forth in claim 5 wherein said contact meanscomprises a pair of contact members and wherein said snap disc directlybridges said contact members to close a fuse circuit.

'7. The invention as set forth in claim 4 wherein said snap disc islocated to flex into switch closing position upon the attainment of apredetermined pressure rise.

8. In a rocket or the like a combustion chamber, a switch chamber in thesaid rocket adjacent thereto, a safety arming switch in said switchchamber and having contact means, an actuating member for engaging saidcontact means to close the switch, said actuating member comprising abimetallic temperature responsive snap disc capable of being flexed intoeither of two dish-shaped forms and forming a part of the wall of thesaid switch chamber, whereby the said snap disc flexes into switchclosing position upon attainment of a predetermined temperature after apredetermined period of fuel combustion in said combustion chamber.

JACOB RABINGW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 578,154 Great Britain June 18, 194.6

